System for testing and adjusting energy levels in the transmission of signals



Dec. 15, 1931. A. 1.. MATTE SYSTEM FOR TESTING AND ADJUSTING ENERGYLEVELS IN THE TRANSMISSION OF SIGNALS Filed Dec. 24, 1928 3 Sheets-Sheet1 \NFWNN QUQN N INVENTOR BY film ATTORNEY Dec. 15, 1931. v A. MATTE1,836,127

SYSTEM FOR TESTING AND ADJUSTING ENERGY LEVELS IN THE TRANSMISSION OFSIGNALS Filed Dec. 24, 1928 3 Sheets-Sheet 2 GIBF L .Zevel Ister InputOutput INVENTOR flllfiztte ATTORNEY Dec. 15, 1931. A. MATTE 1,836,127

SYSTEM FOR TESTING AND ADJUSTING ENERGY LEVELS IN THE TRANSMISSION OFSIGNALS Filed D80. 24, 1928 5 Sheets-Sheet 3 q:- i1 Iii 111w I 1 I I 1 1I I l r 1 x l l Zeqel Ester INVENTOR ATTORNEY Patented Dec. 15, 1931 N T-T L PA NT i O EIY ANDREW L. MATTE, SUMMIT, NEW JERSEY, ASSIGKOR TOAMERICAN TELEPHONE- AND TELEGRAPH COMPANY,-A CORPORATION" OF NEW YORKsYsrEi-z i onrns'rms AND ADJUSTING ENERGY LEVELS In THE rmsmlssrononSIGNALS 1 Application filed December 24, 1928i Serial No. 328,227. 5

An object of my invention is to provide new and improved apparatus and acorresponding method for facilitating the'ad ustment to proper values ofthe energy levels in signal transmitting systems. Another object of myinvention is to provide for automatic testing of the energy level in asignal transmitting system and indication of the resultivenby thetests', Another object'of m invention is to rovide for'makin 'g suchtests and automatically effecting compensatory adjustment tofkeep theenergy level at proper value. Another object of my 1nvention istoprovi-de for the use of one energy level tester for a plurality ofcircuits or channels, These-objects and v'ariousother objects of myinvention will become apparent on consideration of a limited number ofspecific examples of the invention-which I- have chosen to present inthe accompanying drawings and the following specification. It will beunderstood that this disclosure relates principally to these examples ofthe lnventlon and that the scope of the invention will be indicated inthe appended claims.

Referring to the drawings, Figure 1 is a diagram showing my inventioninconnection with a multiplex telegraph system; Fig. 2 is a diagramshowing further how the apparatus of Fig. 1 may be employed; Fig. 3 is adiagram showing the use of my invention-in connection with telephonecircuits; and Figs. 4 and 5 are diagramsshowing how my improvedautomatic potentiometer may be used ent frequencies within the voicefrequency range. Their output currents are controlled by the respectivesenders K and go through respective band filters BF each of appropriatenarrow frequency range and are superposed on the line L. At thereceiving end,

the currents are separated by corresponding band filters BF and go torespective receivers R, with respective associated Sounders Sdj: Onesuch receiving band filter BFisshown in F ig. l with its receiver R andsounder Sd.

Fig. 1 shows a level tester at the bottom, a patrolling device at themiddle ofthe figure, and anautomatic potentiometer? at the top. Thisautomatic potentiometer isas.-

sociated with the branch receiving circuit C The level tester isconnectedin'cyclic order b the-patrolling devicewith various branchreceiving circuits, such as C and tests' the energy level in eachcircuit to which itisconnected and automatically effects adjustment ofthe corresponding potentiometer, if that is required. i

a The structure of the apparatus will become,

apparent on consideration of the following description of its operationin sequential; or-

der. Suppose the brushes of the p'atrolli'iig device havepreviouslyreached; and made the contacts shown in Fig.1. Y Thus,- the cir cuit isestablished from one side of the line C through the potentiometer brushA, ;the

patrolling switch bank HD'and the primary of the repeating coil'in thelevel detector LD to ground. The other side of the "branchcin cuit G2being grounded, this puts the repeating coil referred to in parallelwith the rs; ceiver R shown at the upper part of Fig.- 1. Theleveldetector L1) is constructed of high impedance so that itsconnectionin parallel with the normal receiver B does not affect itsoperation.

In the output circuit of the'level detector LD are the windings of-threemarginal relays in series, M, MN-and These are adjusted "so that Moperates 0in any current slightly greater in intensity than the normalinterference found inthe line, MN operates on any current greater thanthe minimum permissible, signaling current desired for the receivingdetector comprised in R, andfMX operates on any current greater than themax imunr current suitable for operation offthat detector. For each ofthese three relays, its operation puts its armature on the respectivecontact M, but when the-corresponding relay Y the battery B through thewinding of release relay RR, switch bank HMN and potentiometer operatingmagnet PMN. The latter magnet will operate and the movement of itsarmatureN will step-the potentiometer arm A to'the right, thus adjustingthe potenti- I ometer P so astoput greater current strength fromtlre.circuit G through the receiving filter 'BF intothe associated detectorcomprised in R and the level detector L1) in parallel therewith. V

As; already noted, the circuit for the magnet. PMN comprises the releaserelay RR which is slowacting. Presently it opens both the pick-up andholding circuits for the relay MNS. whose arma-tu'res fall back, one ofthem opening the vcircuit for" the magnet PMN, traced: heretofore.

If the adjustment of the potentiometer,

made as described above, is suflicient, then immediately uponthatadjustment being made, the current in the leveldetector LD' willincrease enough to operate the relay MN and thusopen'at this relaythepick up circuit for therelay MNS. Eventually in this case. the

release relay ER will close its armature but l lo-effect will followbecause all circuits from theb attery B will now bev open. Onthe otherhand, if the adjustment of the potentiometer P was not enough, then whenthe armature of the release relay RR falls baclgtit will again close thepick-up circuit form'ag-netMNS through the backcontact of relay-MN, andthe cycle of operations will ensue, as before described, and thepotentiometer P will be given another step of adjustment like the firststep, and this action willbe repeated until the potentiometer P has beenadjusted to put enough current into the detector andv the level detectorLD in parallel'therewith so that marginal relay MN wil'l be'operatedwhereupon no further operation ofth'e-relays will ensue. I v We-haVenowconsidered the supposed case wherethe incoming current is too low. ifthe current in the branch circuit C is too strong, then the outputcurrent from the level detector LDwill operate all three of the marginalrelaysrM-fl' MN and MK, thus opening the pick-up circuitv forrelay 'MNSand closing the pick-upcircuit for relay-MXSWhic'h may readily be,traced from battery B through the back contact of the release relay RR,front contact of relay MX, winding of MXS and front contact of relay Mto ground. In

View of the detailed description that has'been 1 level detector LD.

If the incoming current is of proper value, then the output current fromlevel detector LD will operate both marginal relays M and MN, thusopening the pick-up circuitfor relays MNS and MXS so that no suchoperation asdescribed above will take place.

A thermal relay TB is provided with its heating circuit shown closedthrough back contacts on magnet Q and relays MNS'and MXS. With thecurrent flowing in this circuit, the expansible element of thethermalrelay TB is expanded and eventually closes the contact shown'associatedtherewith, thus closing through Q a branch circuit to the one lasttraced. The consequent energization of the magnet Q opens the'circuit oftheheat'ing element of the thermalrelayTR so thatits expansible membercools and contracts and eventually opens the circuitfor the magnet Q.Thus the magnet Q-is energized. periodicallyat intervals of the orderofa' half-minute, say, by the operation of the thermal relay TR,assuming that the armatures of magnets MNS and MX-S remain on their backcontacts. I e Z At'each energization of the magnet Q,the switches HMX,HMN and hi) are stepped along one step. At the beginning o-t our de'--seription of the operation of the apparatus- 1" v 1 V or t 1g. l,weassumed that these switches had just engaged. the terminals with whichthey are shown in contact; this means that the thermal relay TR had justclosed its contactand made the circuit through the magnet Q which inturn had operated to break the'cin, cuit through the heating coil of.the thermal relay TR. Eventually the expansible element of the ther-nial' relay TR will cool off; andcontract so as to open the circuit forthem-agnet Q which, upon its release, will close the circuit for theheating element of TR, provided thearmatures of MNS and MXS are on theirback contacts. Thereupon, the expansible member of thermal relay TR willagain expa l and eventually close the circuit for the magnet all whichwill step the-switchesHM'X,

vHMN and HD along to another set of contactsfor another branch receivingcircuit different from C but similar thereto. That is, the thermal relayTR having connected the switches HMX, HMN and HD for branch receivingcircuit C long-enough for any necoss y adjustments to be made in itspotenti- Y that are found in the circuit of magnet Q, in

Fig. 1 give assurance that the operation of these magnets MNS and MXSshall have been completed as often as required, and that they shall havereleased before the magnet Q,

steps the patrolling switches HD, HMN- and HMX along for connection withanother branch receiving circuit.

Referring to Fig. 2, it will be seen that one level tester and onehunting device can be used. at a station for a plurality of differentlines and channels coming into that station, and these lines andchannels may be more or less independent of each other except that theirreceiving ends are at the one station and all are served by the onelevel tester and patrolling device. U r

Attention is directed to the switchesll in Fig. 1. By closing these, thesystem is put in condition so that whenever a potentiometer adjustmentis required, it will be indicated by the signal lamps or bells 12, andthus an at tendant will be notified of the situation. If desired, at thesame time that the switches 11 are closed, the switches 13 may beopened, thus cutting off the automatic potentiometer and leaving itsadjustment to be performed manuahy by. an attendant guided by thesignals 12 and 13.

The thermalrelay TR may be adjusted as to its period by shifting theheat insulating sleeve SZ. The more this sleeve covers the expansibleelement, the more'slowly will it expand and contract, thus lengtheningthe period of this relay.

Referring to Fig. 3, this shows a system adapted for regulating the gainatrepeaters on telephone transmission lines or any other circuitsequipped with amplifiers or boosters. The boxes marked SR aretelephonesending and receiving stations. The upper line in the figure isa twowire system with22-type repeaters along its length, one of which isshown diagrammatically; others are indicated by the boxes marked 221%.The two conductor pairs marked l-wire belong to a four-wire system withone-way repeaters in each conductor pair. In the 22-type repeaters andin the one-way repeaters, the amplifying elements are. marked X, andeach such amplifying element hasan automatic potentiometer P on itsinput side whereby the intensity of the input to the correspondingamplifier X can be adjusted. Also, it will be seen that a branch circuitis taken oil on the 'output'side of each amplifier X. 'Wherethe dottedlines occur at T in Fig. 3, there will be a system of trunks like thoseshown at the middle of Fig. 1.

One set of conductors to a potentiometer P and from the output side ofthe corresponding amplifier X are shown in- Fig. 8 connected,

down through a patrolling device to' a level tester at the bottom ofFig. 3. Whereas Fig. 1 showed grounded circuits and hence only one sideof the circuit had. to be carried through the patrolling device, Fig. 3shows;

metallic circuits and both sides of-the cirvice. Accordingly, there isone more wiper and set of contacts in the patrolling device of Fig. 3than in Fig. 1,:that is, HDA and HDB in Fig. 3 take the place of HD inFig. 1.

The level tester in Fig. 3 is amade with-a level detector LDin twostages with an adjustable tuned circuit between them at-RC,

The reason for making this level detector LD cuit are carried throughthe patrolling-dd in two stages instead ofin one stage, as in: V

Fig. 1, is so that the level detector LD shall be selective to frequencyand yet offer very high impedance across the transmission line;

At a distance from the repeater X, along the line toward thecorresponding sending station, an oscillatorO isprovided with acorresponding tuned circuit V and its output is applied-to the-line andreceived through the branch circuit on' the output side of the amplifierX. The tunedYcircuit at RC'isj' if tunedto the same frequency, and hencethe" currentof this frequency is detected in the level detector LD andoperatesthe levelt'ester-of Fig. 3 in the same manner as described forFig. 1. I

It will readily be seen that on the'line'trans mitting into theamplifierX takenwith said amplifier, as the overall loss varies,the-intensity of the componentcurrentfof frequency determined bythejapparatusV will also vary,

and this variation'will bedetected in the level detectorLD,'andthe'level tester will be operated accordingly to effectcompensatory ad j ustmentof the corresponding potentiometer P. "Thepatrolling device operates in the testerin cyclic order with variousamplifying units X and their associated adjustable potentiometers'P. Theapparatus ca'ntake care of twenty repeater units, for example, reachingthem in fifteen-minute cycles.

same way as for Fig. 1 to connect the level In the case of a telephonesystem, the test A ing frequency, as determined at V, may be just outs1dethe voice range and continually present, in which case the switchesat 14 will remain closed. Ifthe system is a'multiplex v telegraphsystem, with a plurality of ch'annelsin the voice frequency range,thenjthe' test frequency may be taken midway between twoof the channels.Again, for' telephone transmission, the test frequency may be takenwithin the voice range and applied only at times when the correspondingcircuit is not in use for voice transmission In this case,

the switch 14 will normally be open, but will be closed only when the.testing frequency is tobe applied. "Also, in this case fthe level testerwill leave thecorresponding potentiometer undisturbed while thecircuitisin use for-talking.

WVhile I 'haveillustrated myv invention in the clrawings-for wiretransmission systems, it will be readily understood that it isapplicable for. radio telephone transmission, in

.which case the testfrequency may be taken outside the carrier band andthe receiving that determined by the apparatus V, but the tuning withinthe level detector LD can be made very close and'such a voice componentwill be of comparatively seldom occurrence, and even if itshould on rareoccasions cause the level tester to give a step of adjustment,

' this step of adjustment would soon be corrected by a normaladjustment.

'.In a system such as that shown in Fig. 3, not all the repeaters needbe controlled, but only enough of them to keep the system Within properlimits of energy level throughout.

It should be noticed: that in Fig. 1 the'system is operated according tothe strength of the signaling currents themselves,-and no auxiliarycurrents or channels are required. In all the modifications shown in mydrawings, the adjustment takes care of changes of energy leveldue towhatever cause," whether temperature changes along the line, or changesin the repe'atersor receiving apparatus, or changes in voltage supply. 7I In'caseit is desiredto provide for manual potentiometer adjustment inaddition to the automatic potentiometer adjustment, and with the'twoadjustments more orless independent of each other, this may beaccomplished by means of the apparatus shown in Fig or Fig. 5. In eachof Figs. 1} and there is a two-stage amplifier. In Fig. 4 there is anautomatic potentiometer AP between'the stagesand a manual potentiometerHP on the input side of both stages, but in Fig. 5 thesepotentiometersare interchanged. In Fig; 4 changes in the setting of HPhave the same effect as loss changes in the line connected to the input.If in Fig. 4c, the'power level is tested at T, then I-IP may be adjusted1 to bring the arm of AP to a desired normal,

and AP will be affected by changes in re: peater gain etc. and willcompensate therefor. Referring to Fig. 5-suppose first that the powerlevel is tested at T. This means that the automatic potentiometer APisgoverned by the power level across the line at T and any changesaifectingtransmission beyond T in the direction of transmission arewithout cffecton AP. Hence in this case the manual potentiometer HP willeffect a superposed adjustment of power level at T. This facilitatesmaking compensation for minor differences of gain among difierentdetectors .of a set of telegraph detectors all subject to ad'- just-mentin cyclic order as disclosed earlier in this specification. On the otherhand in Fig. 5, suppose the automatic test of the power level is at T,then the automatic potentiometer AP is controlled by the level at thatpoint, and hence any adjustment of the manual potentiometer HP will leadto an opposite automatic adjustment. of AP. It follows that HP may beadjusted to bring AP to a desired intermediate normal adjustment.

I claim:

1. In combination, a signal transmitting system to be held at a certainstandard energy level at a certain place and subject to a vari able lossfrom that level, an automatic level tester of high impedance, means toconnect said level tester intermittentlyto said system to measurethisless, an adjustable device to compensate the loss,and means controlledby said level tester to effect a compensatory adjustment of said device.I

2. In combination, a signal transmitting s stem subject at a certainpoint therein to variation of energy level, high impedance meansintermittently to connect wlth sald system at this point and test fordepartures from a certain standard level, adjustable means to bring thelevel to the standard, and means controlled by said testing means toeffect suitable adjustment of said level ad j usting means. i

3. In combination, a plurality of signal transmitting systems each to bemaintained at a respective proper energy level,respectivepotentiometers, a level tester, and'a patrolling device to connect thelevel tester to the said systems in cyclic order to testthem fordepartures from their properlevel and also to connect the level testerto the correspond ing potentiometers to adjust them to keep the levelsat their proper values, said level tester being constructed so that itsconnection to said systems will not alter the line conditions of thesystemsa't any useful frequency.

4. In combination, a signal transmitting system subject at a certainpoint therein to variation of energy level, a set of marginal relaysconnected to be actuated according to the said energy level withoutsubstantially altering the operative condition of the system, whetherconnected or not, a potentiometer in said system, and means to operatesaid potentiometer by said marginal relays.

5. Incombination, a plurality of signal transmitting systems, each to bemaintained at a respective proper energy level, respectivepotentiometers, a set of marginal relays, means to connect-this set ofrelays in cyclic order with said systems and at each such connection tooperate them according to. the

energy level in the connectedsystem, said means beingadapted to preservethe operative condition of the systems unchanged by reason of theconnection, and means to operate the corresponding potentiometer by saidmarginal relays.

6. In combination, a signal transmitting system, an automatic leveltester to test the power level of signaling currents at a certain pointin said system without substantial reaction in the system, meansintermittently to connect said level tester to the system and anautomatic potentiometer controlled by said tester to effect compensatoryadjustment for departures of said level from a standard value.

7. In a signaling system subject to inter mittent transmission ofelements of signal.

current, high impedance means to test the power level in such elementsunaffected by intervening condltlons of no transmission of signalelements, means intermittently to con-- nect said testing means to thesaid system, and a potentiometer controlled by said testing means toeffect compensatory adjustment for departures of said level from astandard value.

8. In a signal system, means for putting signal currents through thesystem, means for putting other superposed currents through the system,high impedance means for testing the power level of the said othercurrents unaffected by the signal currents, and a potentiometercontrolled by said last mentioned means.

9. In an alternating current system subject to variation of voltagelevel at a certain point, automatic high impedance means to test thevoltage level at that point for departure thereof from a standard value,means to connect said automatic testing means to the systemintermittently, and means to effect a compensatory adjustment to holdthe voltage level at said standard value, said adjusting means beingcontrolled by said testing means.

i 10. In combination, a plurality of signal transmitting systems,respective adjustable means to vary the level in the said systems, ahigh impedance automatic level tester, and means to connect it in cyclicorder to test the departure of the levels in said systems from normaland thereby to effect compensatory adjustments of said adjustable meansso as to 7 hold said levels near normal. 7 11. A plurality ofalternating current systems each subject to variation of power level ata certain place, respective means to effect compensatory adjustments fordepartures of level from normal values, and high impedance means to testthe levels 1n cyclic order and thereby to make the adjustments to holdsaid levels near normal.

In testimony whereof, I have signed my name to this specification this17th day of December, 1928. 7

ANDREW L. MATTE.

